/* Taken from utexas-art-ros-pkg:art_vehicle/applanix */

/*
 * Conversions between coordinate systems.
 *
 * Includes LatLong<->UTM.
 */

#ifndef _GPS_CONV_H
#define _GPS_CONV_H

/**  @file

     @brief Universal Transverse Mercator transforms.

     Functions to convert (spherical) latitude and longitude to and
     from (Euclidean) UTM coordinates.

     @author Chuck Gantz- chuck.gantz@globalstar.com

 */

#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <iostream>

namespace gps_conv
{
const double RADIANS_PER_DEGREE = M_PI/180.0;
const double DEGREES_PER_RADIAN = 180.0/M_PI;

// WGS84 Parameters
const double WGS84_A = 6378137.0;       // major axis
const double WGS84_B = 6356752.31424518;    // minor axis
const double WGS84_F = 0.0033528107;        // ellipsoid flattening
const double WGS84_E = 0.0818191908;        // first eccentricity
const double WGS84_EP = 0.0820944379;       // second eccentricity

// UTM Parameters
const double UTM_K0 = 0.9996;           // scale factor
const double UTM_FE = 500000.0;     // false easting
const double UTM_FN_N = 0.0;            // false northing on north hemisphere
const double UTM_FN_S = 10000000.0;     // false northing on south hemisphere
const double UTM_E2 = (WGS84_E*WGS84_E);    // e^2
const double UTM_E4 = (UTM_E2*UTM_E2);      // e^4
const double UTM_E6 = (UTM_E4*UTM_E2);      // e^6
const double UTM_EP2 = (UTM_E2/(1-UTM_E2)); // e'^2

/**
 * Utility function to convert geodetic to UTM position
 *
 * Units in are floating point degrees (sign for east/west)
 *
 * Units out are meters
 */
static inline void UTM(double lat, double lon, double *x, double *y)
{
  // constants
  const static double m0 = (1 - UTM_E2/4 - 3*UTM_E4/64 - 5*UTM_E6/256);
  const static double m1 = -(3*UTM_E2/8 + 3*UTM_E4/32 + 45*UTM_E6/1024);
  const static double m2 = (15*UTM_E4/256 + 45*UTM_E6/1024);
  const static double m3 = -(35*UTM_E6/3072);

  // compute the central meridian
  int cm = ((lon >= 0.0)
        ? ((int)lon - ((int)lon)%6 + 3)
        : ((int)lon - ((int)lon)%6 - 3));

  // convert degrees into radians
  double rlat = lat * RADIANS_PER_DEGREE;
  double rlon = lon * RADIANS_PER_DEGREE;
  double rlon0 = cm * RADIANS_PER_DEGREE;

  // compute trigonometric functions
  double slat = sin(rlat);
  double clat = cos(rlat);
  double tlat = tan(rlat);

  // decide the false northing at origin
  double fn = (lat > 0) ? UTM_FN_N : UTM_FN_S;

  double T = tlat * tlat;
  double C = UTM_EP2 * clat * clat;
  double A = (rlon - rlon0) * clat;
  double M = WGS84_A * (m0*rlat + m1*sin(2*rlat)
            + m2*sin(4*rlat) + m3*sin(6*rlat));
  double V = WGS84_A / sqrt(1 - UTM_E2*slat*slat);

  // compute the easting-northing coordinates
  *x = UTM_FE + UTM_K0 * V * (A + (1-T+C)*pow(A,3)/6
                  + (5-18*T+T*T+72*C-58*UTM_EP2)*pow(A,5)/120);
  *y = fn + UTM_K0 * (M + V * tlat * (A*A/2
                      + (5-T+9*C+4*C*C)*pow(A,4)/24
                      + ((61-58*T+T*T+600*C-330*UTM_EP2)
                     * pow(A,6)/720)));

  return;
}

/**
 * Determine the correct UTM letter designator for the
 * given latitude
 *
 * @returns 'Z' if latitude is outside the UTM limits of 84N to 80S
 *
 * Written by Chuck Gantz- chuck.gantz@globalstar.com
 */
static inline char UTMLetterDesignator(double Lat)
{
    char LetterDesignator;

    if     ((84 >= Lat) && (Lat >= 72))  LetterDesignator = 'X';
    else if ((72 > Lat) && (Lat >= 64))  LetterDesignator = 'W';
    else if ((64 > Lat) && (Lat >= 56))  LetterDesignator = 'V';
    else if ((56 > Lat) && (Lat >= 48))  LetterDesignator = 'U';
    else if ((48 > Lat) && (Lat >= 40))  LetterDesignator = 'T';
    else if ((40 > Lat) && (Lat >= 32))  LetterDesignator = 'S';
    else if ((32 > Lat) && (Lat >= 24))  LetterDesignator = 'R';
    else if ((24 > Lat) && (Lat >= 16))  LetterDesignator = 'Q';
    else if ((16 > Lat) && (Lat >= 8))   LetterDesignator = 'P';
    else if (( 8 > Lat) && (Lat >= 0))   LetterDesignator = 'N';
    else if (( 0 > Lat) && (Lat >= -8))  LetterDesignator = 'M';
    else if ((-8 > Lat) && (Lat >= -16)) LetterDesignator = 'L';
    else if((-16 > Lat) && (Lat >= -24)) LetterDesignator = 'K';
    else if((-24 > Lat) && (Lat >= -32)) LetterDesignator = 'J';
    else if((-32 > Lat) && (Lat >= -40)) LetterDesignator = 'H';
    else if((-40 > Lat) && (Lat >= -48)) LetterDesignator = 'G';
    else if((-48 > Lat) && (Lat >= -56)) LetterDesignator = 'F';
    else if((-56 > Lat) && (Lat >= -64)) LetterDesignator = 'E';
    else if((-64 > Lat) && (Lat >= -72)) LetterDesignator = 'D';
    else if((-72 > Lat) && (Lat >= -80)) LetterDesignator = 'C';
        // 'Z' is an error flag, the Latitude is outside the UTM limits
    else LetterDesignator = 'Z';
    return LetterDesignator;
}

/**
 * Convert lat/long to UTM coords.  Equations from USGS Bulletin 1532
 *
 * East Longitudes are positive, West longitudes are negative.
 * North latitudes are positive, South latitudes are negative
 * Lat and Long are in fractional degrees
 *
 * Written by Chuck Gantz- chuck.gantz@globalstar.com
 */
static inline void LLtoUTM(const double Lat, const double Long,
                           double &UTMNorthing, double &UTMEasting,
                           char* UTMZone)
{
    double a = WGS84_A;
    double eccSquared = UTM_E2;
    double k0 = UTM_K0;

    double LongOrigin;
    double eccPrimeSquared;
    double N, T, C, A, M;

        //Make sure the longitude is between -180.00 .. 179.9
    double LongTemp = (Long+180)-int((Long+180)/360)*360-180;

    double LatRad = Lat*RADIANS_PER_DEGREE;
    double LongRad = LongTemp*RADIANS_PER_DEGREE;
    double LongOriginRad;
    int    ZoneNumber;

    ZoneNumber = int((LongTemp + 180)/6) + 1;

    if( Lat >= 56.0 && Lat < 64.0 && LongTemp >= 3.0 && LongTemp < 12.0 )
        ZoneNumber = 32;

        // Special zones for Svalbard
    if( Lat >= 72.0 && Lat < 84.0 )
    {
      if(      LongTemp >= 0.0  && LongTemp <  9.0 ) ZoneNumber = 31;
      else if( LongTemp >= 9.0  && LongTemp < 21.0 ) ZoneNumber = 33;
      else if( LongTemp >= 21.0 && LongTemp < 33.0 ) ZoneNumber = 35;
      else if( LongTemp >= 33.0 && LongTemp < 42.0 ) ZoneNumber = 37;
     }
        // +3 puts origin in middle of zone
    LongOrigin = (ZoneNumber - 1)*6 - 180 + 3;
    LongOriginRad = LongOrigin * RADIANS_PER_DEGREE;

    //compute the UTM Zone from the latitude and longitude
    snprintf(UTMZone, 4, "%d%c", ZoneNumber, UTMLetterDesignator(Lat));

    eccPrimeSquared = (eccSquared)/(1-eccSquared);

    N = a/sqrt(1-eccSquared*sin(LatRad)*sin(LatRad));
    T = tan(LatRad)*tan(LatRad);
    C = eccPrimeSquared*cos(LatRad)*cos(LatRad);
    A = cos(LatRad)*(LongRad-LongOriginRad);

    M = a*((1   - eccSquared/4      - 3*eccSquared*eccSquared/64    - 5*eccSquared*eccSquared*eccSquared/256)*LatRad
                - (3*eccSquared/8   + 3*eccSquared*eccSquared/32    + 45*eccSquared*eccSquared*eccSquared/1024)*sin(2*LatRad)
                                    + (15*eccSquared*eccSquared/256 + 45*eccSquared*eccSquared*eccSquared/1024)*sin(4*LatRad)
                                    - (35*eccSquared*eccSquared*eccSquared/3072)*sin(6*LatRad));

    UTMEasting = (double)(k0*N*(A+(1-T+C)*A*A*A/6
                    + (5-18*T+T*T+72*C-58*eccPrimeSquared)*A*A*A*A*A/120)
                    + 500000.0);

    UTMNorthing = (double)(k0*(M+N*tan(LatRad)*(A*A/2+(5-T+9*C+4*C*C)*A*A*A*A/24
                 + (61-58*T+T*T+600*C-330*eccPrimeSquared)*A*A*A*A*A*A/720)));
    if(Lat < 0)
        UTMNorthing += 10000000.0; //10000000 meter offset for southern hemisphere
}

static inline void LLtoUTM(const double Lat, const double Long,
                           double &UTMNorthing, double &UTMEasting,
                           std::string &UTMZone) {
  char zone_buf[] = {0, 0, 0, 0};

  LLtoUTM(Lat, Long, UTMNorthing, UTMEasting, zone_buf);

  UTMZone = zone_buf;
}

/**
 * Converts UTM coords to lat/long.  Equations from USGS Bulletin 1532
 *
 * East Longitudes are positive, West longitudes are negative.
 * North latitudes are positive, South latitudes are negative
 * Lat and Long are in fractional degrees.
 *
 * Written by Chuck Gantz- chuck.gantz@globalstar.com
 */
static inline void UTMtoLL(const double UTMNorthing, const double UTMEasting,
                           const char* UTMZone, double& Lat,  double& Long )
{
    double k0 = UTM_K0;
    double a = WGS84_A;
    double eccSquared = UTM_E2;
    double eccPrimeSquared;
    double e1 = (1-sqrt(1-eccSquared))/(1+sqrt(1-eccSquared));
    double N1, T1, C1, R1, D, M;
    double LongOrigin;
    double mu, phi1Rad;
    double x, y;
    int ZoneNumber;
    char* ZoneLetter;

    x = UTMEasting - 500000.0; //remove 500,000 meter offset for longitude
    y = UTMNorthing;

    ZoneNumber = strtoul(UTMZone, &ZoneLetter, 10);
    if((*ZoneLetter - 'N') < 0)
    {
        y -= 10000000.0;//remove 10,000,000 meter offset used for southern hemisphere
    }

    LongOrigin = (ZoneNumber - 1)*6 - 180 + 3;  //+3 puts origin in middle of zone

    eccPrimeSquared = (eccSquared)/(1-eccSquared);

    M = y / k0;
    mu = M/(a*(1-eccSquared/4-3*eccSquared*eccSquared/64-5*eccSquared*eccSquared*eccSquared/256));

    phi1Rad = mu    + (3*e1/2-27*e1*e1*e1/32)*sin(2*mu)
                + (21*e1*e1/16-55*e1*e1*e1*e1/32)*sin(4*mu)
                +(151*e1*e1*e1/96)*sin(6*mu);

    N1 = a/sqrt(1-eccSquared*sin(phi1Rad)*sin(phi1Rad));
    T1 = tan(phi1Rad)*tan(phi1Rad);
    C1 = eccPrimeSquared*cos(phi1Rad)*cos(phi1Rad);
    R1 = a*(1-eccSquared)/pow(1-eccSquared*sin(phi1Rad)*sin(phi1Rad), 1.5);
    D = x/(N1*k0);

    Lat = phi1Rad - (N1*tan(phi1Rad)/R1)*(D*D/2-(5+3*T1+10*C1-4*C1*C1-9*eccPrimeSquared)*D*D*D*D/24
                    +(61+90*T1+298*C1+45*T1*T1-252*eccPrimeSquared-3*C1*C1)*D*D*D*D*D*D/720);
    Lat = Lat * DEGREES_PER_RADIAN;

    Long = (D-(1+2*T1+C1)*D*D*D/6+(5-2*C1+28*T1-3*C1*C1+8*eccPrimeSquared+24*T1*T1)
                    *D*D*D*D*D/120)/cos(phi1Rad);
    Long = LongOrigin + Long * DEGREES_PER_RADIAN;

}

static inline void UTMtoLL(const double UTMNorthing, const double UTMEasting,
    std::string UTMZone, double& Lat, double& Long) {
  UTMtoLL(UTMNorthing, UTMEasting, UTMZone.c_str(), Lat, Long);
}
} // end namespace UTM

#endif // _UTM_H
